WASHINGTON — A former Air Force sergeant who defected to Iran did severe damage to American intelligence operations, and is suspected of revealing the names of double agents run by United States military intelligence, some of whom had their cover blown after her defection, according to former counterintelligence officials.

Monica Elfriede Witt, 39, the former Air Force counterintelligence agent, is also accused of exposing the names of eight American military counterespionage agents, and she had knowledge of how the United States intercepted foreign communications, the government’s most important stream of intelligence. She also knew the inner workings of American military operations across the Middle East.

Ms. Witt’s indictment on charges of providing American secrets to Tehran was made public this week. Her alleged activities came at a time when American intelligence operations were already plagued by the penetration of a top-secret communications network by China and Iran that had deeply damaged spying operations abroad.

When Ms. Witt defected to Iran in August 2013, “defensive measures” were taken in an attempt to reduce the damage she could inflict, according to a former senior intelligence official who spoke on the condition of anonymity, like others involved in the case, because of its sensitivity.

One former senior intelligence official who discussed the case publicly, Douglas H. Wise, said that by the time he took over as deputy director of the Defense Intelligence Agency, a year after Ms. Witt’s defection, American authorities were bracing for the worst.

“We knew this was going to end badly,” Mr. Wise said. “On a scale of one to 10, I believed she was a seven or eight in terms of the potential for doing damage to the United States.”

The indictment of Ms. Witt, along with interviews of former officials, offers new insight into how much damage American intelligence efforts against Iran suffered in the years before the international nuclear deal was signed in 2015.

Inside the most critical adversarial countries — Iran, China and Russia — the United States’ on-the-ground intelligence has been hurt by defectors, as well as by penetrations of systems used by intelligence officials to communicate with spies overseas, resulting in the death or capture of people helping the United States.

Indictments are often written to put alleged traitorous acts in the worst possible light. But former officials involved in the damage assessments of Ms. Witt say that, if anything, the indictment plays down the damage that the former counterintelligence agent did, perhaps to prevent further compromise of individuals or operations.

Ms. Witt, a former Air Force tech sergeant who worked with the service’s counterintelligence office, would have had little or no insight into the Central Intelligence Agency’s informants in Iran, officials said. But she had knowledge of classified intelligence efforts by the military intelligence services, the F.B.I. and the Defense Intelligence Agency.

As a result, Ms. Witt had access to “the true names of intelligence sources and clandestine agents,” according to the indictment. She also had names of the intelligence officers who recruited those sources.

The damage assessment after Ms. Witt’s defection could not determine definitively if she gave up the names of double agents, but the former official said their covers were subsequently blown.

The indictment states that she gave up the identity of her fellow Air Force counterintelligence agents to Iran, allowing Tehran to subject the military service members to cyberattacks after her August 2013 defection.

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Members of Iran’s Islamic Revolutionary Guards Corps, which Ms. Witt is accused of defecting to Iran in August 2013 to work with.CreditAbedin Taherkenareh/EPA, via Shutterstock

In her Air Force intelligence career, Ms. Witt deployed to sensitive areas, including an important military base in Qatar as well as to other parts of the Middle East, expanding the depth of her knowledge of military intelligence efforts in the region.

Ms. Witt did not have access to C.I.A. intelligence or the names of the agency’s informants and agents, officials said. The C.I.A.’s network inside Iran is the most important American asset for determining the status of Tehran’s nuclear and missile programs.

But the damage Ms. Witt caused came as another intelligence failure was being brought to light inside the agencies: the penetration of the secret internet-based network the C.I.A. used to communicate with informants in Iran, China, Russia and elsewhere.

The collapse of the covert communications network, called the “covcom” by intelligence agencies, led to the deaths of informants in Iran, intelligence officials assessed. It also forced the C.I.A. to resettle others who had provided assistance to the agency.

In addition, the compromise of the network led to the loss of informants in China, where the C.I.A.’s network was devastated. Former intelligence officials put some of the blame for those losses in China on a former C.I.A. officer named Jerry Chun Shing Lee, who was arrested and charged with conspiring to commit espionage. In Russia, the agency also suffered setbacks.

Together, the compromise of those networks of informants has been one of the gravest losses of intelligence operatives since the end of the Cold War.

Damage to a spy network takes years, or even decades, to repair. The exposure of the communications system and Ms. Witt’s defection came at a critical time for the United States, just as it was negotiating the nuclear deal with Tehran. Both before that agreement was signed in 2015 and in the years since, the state of Iran’s nuclear program has been a critical issue for intelligence officers.

Former officials said that beyond the information Ms. Witt was allowed to look at with her clearance, there was other classified information she was not supposed to have but might have picked up.

“With her defection, Ms. Witt provided information to the government of Iran that placed sensitive and classified U.S. national defense and intelligence secrets at serious risk,” said Jay Tabb, who heads the F.B.I.’s national security branch.

Once in Iran, Ms. Witt would most likely have been asked by officials to share what she knew about the methods and tradecraft used by American intelligence, said Mr. Wise, the former top deputy at the Defense Intelligence Agency.

“She could have helped them connect the dots and make sense of what they would not likely be able to make sense on their own,” Mr. Wise said. “She would have been extraordinarily valuable to them.”

Officials note that unless Ms. Witt leaves Iran, prosecutors will never have a chance to bring her before a judge for trial.

Former prosecutors say she may someday relax her guard, travel outside Iran and allow an American ally to apprehend her. The odds of that happening are low, but officials point to the case of Mr. Lee returning the United States, shocking those involved in the investigation who thought the former C.I.A. officer would never return. At the time, Mr. Lee was living in Hong Kong.

But even if Ms. Witt is never brought to court, officials said, her indictment should be a warning, and may serve as a deterrent, to others.

“It can be important to call out a traitor,” said David Kris, a former head of the Justice Department’s national security division and founder of the Culper Partners consultancy. “It is part of the public education and a way of saying we know what you did.”